Vacuum producing means and method

ABSTRACT

A vacuum producing method and means to be submerged and secured below the surface of a body of flowing water and comprising a casing with converging axial passage means forming a waterway, and an annular channel communicating with and supplying air to a restricted portion of said waterway.

United States Patent Ziegler [54] VACUUIVI PRODUCING NIEANS AND METHOD[72] Inventor: Charles'l'homas Ziegler, 14242 Victory Boulevard, VanNuys, Calif. 91401 [22] Filed: April 13, 1970 [21] Appl. No.: 32,480v

Related US. Application Data [60] Division of Ser. No. 804,544, March 5,1969,

Pat. No. 3,550,610, which is a continuation-inpart of Ser. No. 698,958,Jan. 18, 1968, abandoned.

[52] US. Cl ..261/25, 61/1 R, 61/20, 261/78 A, 261/121 R, 261/DIG. 75,210/170 [51] Int. Cl. ..B01f 3/04 [58] Field of Search ..261/25, 76-78,

261/78 A, 120-124, DIG. 75; 210/170, 198, 199, 220, 221, 63; 61/1, 2,19,20

[56] References Cited UNITED STATES PATENTS 3,365,178 1/1968 Bood..261/25 51 Nov. 28, 1972 2/1903 Gwynne et a1 ..261/77 1,623,369 4/1927Till ..61/2 3,336,016 I 8/ 1967 Schreiberm. ..210/220 X 3,151,190 9/1964Kapitula ..261/78 R FOREIGN PATENTS OR APPLICATIONS 1,377,571 9/1964France ..210/220 942,754 11/1963 Great Britain ..210/63 96,928 12/1923Austria ..61/19 1,163,168 9/1958 France ..61/1 R 1 1 1,431 8/1925Switzerland ..61/ 19 OTHER PUBLICATIONS Great Britain Water PollutionResearch Board, 1959 Report, pps. 94-98.

Primary Examiner--Tim R. Miles [57] ABSTRACT A vacuum producing methodand means to be submerged and secured below the surface of a body offlowing water and comprising a casing with converging axial passagemeans forming a waterway, and an annular channel communicating with andsupplying air to a restricted portion of said waterway.

20 Claims, 5 Drawing Figures PATENTEUmJv 28 m2 SHEET 1 or 3 A 'romvrvgPATENTEDNB 28 I972 13. 704,008

SHEET 2 OF 3 INVENTOR. 040 77600 1/47/0- ATTORNEY;

VACUUM PRODUCING MEANS AND METHOD This application is a division ofapplication Ser. No. 804,544, filed Mar. 5, 1969, now U. S. Pat. No.3,550,610, which in turn is a Continuation-in-part of my applicationentitled VACUUM PRODUCING MEANS, Ser. No. 698,958, filed Jan. 18, 1968,now

abandoned.

This invention relates to an apparatus and method of producing a vacuumutilizing the natural flow of fluid, and relates more particularly to atunnel structure or casing formed with a passage or waterway ofdecreasing diameter from end to end, the casing being immersed in a bodyof flowing water. This body of water may be an inland stream or may betidal water. The velocity of flow through the casing is accelerated fromthe larger inlet end to a smaller discharge or nozzle end to produce avacuum capable of drawing large quantities of air from the atmosphereinto the stream for a variety of purposes such as purifying the water byincorporating oxygen into the water.

An important object of the invention is to provide an improved apparatusfor the aeration of flowing bodies of water. Streams become so pollutedwith chemicals and sewage that aquatic life cannot be supported, dueprimarily to the reduced oxygen content. The waste chemicals combinereadily with oxygen, however, and the apparatus of the present inventionreplenishes the oxygen. It is also important to note that oxygenation ofmost waste chemicals renders them harmless. The apparatus of the presentinvention can also be used in bays that are subjected to tidalvariations for aerating the water flowing into the bay where lobsterraising operations exist.

One embodiment of the invention includes a casing having an inlet endand a discharge end, the casing being suitably anchored in the stream bymeans sufficiently strong to prevent it from moving downstream from itsoperating position and also to resist a twisting movement which theflowing water tends to impart to it. The continuous passage or waterwaymay be of a special configuration that includes one or more tunnelsections or runs of substantially uniform diameter. If there is morethan one run, each successive run is smaller than the preceding run, andbetween these successive runs there is an expansion chamber, eachsucceeding expansion chamber being smaller than the preceding one.

The inlet end is of tapered contour and is preferably formed withconcavely curved walls and with a lesser diameter at its lower end whichjoins with the first run. The last run is connected with an exit tunnelforming a nozzle end that is of slightly larger diameter than the lastrun. The casing is also formed with an elongated annularvacuum-producing chamber that surrounds the passage through the casing.This annular chamber is joined at its lower end with the water passagebetween the last run and the nozzle end and the vacuum is produced inthe annular chamber by the accelerated velocity of the water. A conduitextends from the vacuum chamber to the atmosphere above the level of theflowing water. The vacuum in this conduit may be used for a variety ofpurposes as previously mentioned. This first embodiment serves as meansto aerate the body of flowing water and other simpler embodiments of theinvention are employed for the same purpose.

Another embodiment of the invention is submerged in a stream of waterthat periodically reverses its direction of flow, for example tidewater.The submerged device aerates the water flowing therethrough inthealternate opposite direction and automatically adapts itself to thedirection of flow. 1

In the drawings:

FIG. 1 isa perspective view of a longitudinal section taken through thecasing of the first embodiment of the invention;

FIG. 2 is a central section taken through a modified form of theinvention;

FIG. 3 shows another modified form;

FIG. 4 shows another modified form; and

FIG. 5 is an embodiment of the invention for use in a body of water thatflows alternately in opposite directions, the embodiment beingreversable in function to function in both directions.

The casing 10 shown in FIG. 1, which may be molded or cast from concreteor other suitable material, has an outer cylindrical surface 11 and hasa water passage 14 extending therethrough from end to end. At a pointdownstream from the inlet end, there is a first tunnel section or run 18which is shown in FIG. 1 as being of substantially uniform diameter.Between the inlet end 12 and this first tunnel section 18 is an inletsection which is funnel shaped and preferably has curved walls whichtaper downstream. The inlet section has its smallest diameter at 16where it joins with the first tunnel section 18 which leads to anexpansion chamber 19 of larger diameter than the tunnel section andwhich may have a generally spherical contour.

A second run 20 adjacent the expansion chamber 19 has a lesser diameterthan the first run 18 and this second run leads to a second expansionchamber 21 somewhat shorter than the first expansion chamber 19 and alsoformed with concavely curved walls. A third tunnel section 22 of stilllesser diameter leads to an exit section or nozzle 24 of slightlygreater diameter.

An annular chamber 26 surrounding'the passage 14 is formed in the casing10 and the downstream end of this annular chamber shown at 28communicates with an annular zone between the tunnel section'22 and thenozzle 24. The annular chamber 26 preferably extends back a reasonabledistance towards the inlet end of the casing and serves as a vacuumchamber, the vacuum being caused by the venturi effect of flow of thefluid into the nozzle 24. A conduit 29 extends from the vacuum chamber26 through an opening 30 in the casing wall and into the atmosphereabove the level of the body of water. The velocity of the water enteringthe inlet end of the casing 10 is constant and by virtue of theprogressive reduction of the cross-sectional area of the passage 14there is a rapid acceleration of the speed of flow by the time the waterreaches the annular zone at the opening 28 of the vacuum chamber 26where the flowing water enters the slightly large nozzle 24. Thequantity of air drawn into the vacuum chamber 26 can be very large.

FIG. 2 shows a casing 34 with a passage therethrough, wherein the firstinlet section of the passage has a gradual taper to its lower end 38where the inlet section joins a first tunnel section 39. Section 40, 41and 42 are similar to the corresponding sections 19, 20 and 21 ofFIG. 1. The annular space 44 between a last tunnel section 46 and afinal nozzle section 48 communicates with a vacuum chamber 49 that inturn communicates withthe atmosphere.

The casing of FIG. 3 has runs 51 and 52 which preferably are curved incross section rather than straight and the inner end 54 of the firstinlet section 56 is substantially smaller than the entrance to the inletsection. This figure also showsa vacuum chamber 58 of greater relativevolume than the vacuum chambers that are shown in H68. 1 and 2.

FIG. 4 shows a more basic arrangement with a single run 60 between atapered inlet section 61 and a tapered section 62. An annular space 64between the tapered section 62 and a final nozzle section 65communicates with a vacuum chamber 66 which in turn communicates withthe atmosphere.

It is apparent that-each of the forms of the invention shown in FIGS. 14 functions with a venturi action that is highly effective for drawingair from the atmosphere for entrainment in a flowing body of water. inall of the embodiments the diameter of the water passage through thecasing is reduced at a final nozzle section to approximately one-half orless of the inlet diameter. it is tobe noted that in the selectedembodiments of the invention the final nozzle section dischargesdirectly into the surrounding body of water and that by preference thelength of the final nozzle section is not more than approximately 20percent of the total length of the casing. The reduction in the crosssection of the passage through the casing causes relatively highacceleration of the velocity of the stream through the casing in thezone at the upstream end of the discharge nozzle. The acceleration ofthe stream of water results in drop of the static pressure of the waterin this zone to substantially below atmospheric pressure with theconsequence that a vacuum is created in the zone and in the associatedannular vacuum chamber.

H6. shows an embodiment of the invention in which a casing 70 issubmerged in a body of water that periodically reverses its direction offlow, for example tidewater in a tidal basin or in off shore water wherethe current periodically reverses. The casing '70 which may be suitablyelevated from the bottom of the water by support structure 72 and thecasing may be made in separable sections for the purpose of fabricationand for the purpose of access to its interior when desired.

The casing 70 forms a passage lontigudinally therethrough which includesan inwardly convergent passage section 74 at one end and a similarinwardly convergent passage section 75 at the other end, the twosections being suitably dimensioned with a suitable angle ofconvergence. The inwardly convergent section 74 adjoins a first necksection 76 and the convergent section 75 adjoins similar second necksection 78. In the region of the longitudinal center of the casing 70,there is a restricted central intermediate section 80 of the waterpassage, the restricted section being formed by a body of concrete 82.

The body of concrete 82 is positioned inside an annular chamber 84 andis suitably supported in the annular chamber by a plurality ofspoke-like radial elements 85. The annular chamber 84 is a vacuumchamber and accordingly is in communication with the atmosphere througha standpipe 86 that extends above the level of the surrounding water andis equipped with a suitable conical shield 87 to prevent foreign matterfrom dropping into the vacuum chamber. One end of the vacuum chamberforms a first annular section 88 of .the passage through the casing andthe other end of the vacuum chamber forms a second annular section 89 ofthe passage.

A first tubular shuttle 90 is mounted in the first neck section 76 and asimilar second tubular shuttle 92 is mounted in the second neck section78, each of the two shuttles being slidingly mounted for longitudinalmovement in response to impingement of flowing water thereon. The innerend of each of the two shuttles is formed with a conical flange 94shaped and dimensioned to mate with the corresponding conical end of theconcrete body 82 and thc outer end of each tubular shuttle is providedwith a similar conical flange 95.

Each of the two tubular shuttles is longitudinally movable between afirst retracted position and a second advanced position. In FIG. 5 thefirst shuttle 76 is at its retracted position where the retractingmovement of the shuttle is limited by abutment of the conical flange 95of the shuttle with the inner end of the first neck section 76 of thepassage. The second shuttle 78 is shown at its advanced position whereit extends across the second annular section 89 of the passage in directcommunication with the restricted central secdonof the passage.

In FIG. 5 the current is flowing from the rightend of the casing to theleft end and the impingement of the current against the outer conicalflange 95 of the second shuttle 92 has moved the second shuttle to itsadvanced position. The current flowing in the same direction hasimpinged on the inner conical flange 94 of the first shuttle to retractthe first shuttle. It will be noted that the cross section of theentering current is initially reduced to the cross section of the secondshuttle 92 and then is stepped down by the restricted central section 80of the passage. Consequently the stream of water through the casingreaches maximum velocity in the central section 80 and then isdischarged across the first annular section 88 of the passage into thefirst shuttle 90. The resulting venturi effect draws air from theatmosphere through the standpipe 86 and through the vacuum chamber 84into entrainment with the water flowing through the casing 70.

When the direction of water flow through the casing 70 is subsequentlyreversed, the impingement of the water against the conical flange of thefirst shuttle 90 advances the first shuttle into engagement with theconcrete body '82 and the impingement of the water against the innerconical flange 94 of the second shuttle 92 retracts the second shuttleso that the accelerated stream of water crosses the second annularsection 89 of the water passage with consequent entrainment of air inthe water.

My description in specific detail of the selected embodiments of theinvention will suggest various changes, substitutions and otherdepartures from my disclosure. l

1 claim:

1. In a device for aerating open water that periodically flows inopposite directions, for example tidewater, the combination of:

a casing submerged in the open water in longitudinal alignment with theopposite directions of flow,

with consequent reduction of the static pressure of l the water in theintermediate zone to substantially below atmospheric pressure; and

means placing said intermediate zone in communication with theatmosphere for air flow from the atmosphere into entrainment in thewater in the intermediate zone.

2. In a device for aerating open water that periodically flows inopposite directions, for example tidewater, the combination of:

a casing submerged in the open water in longitudinal alignment with theopposite directions of flow,

said casing having a longitudinal passage therethrough for oppositedirections of flow therethrough in response to the opposite directionsof flow of the open water,

said passage being of relatively large cross section at its oppositeends and narrowing in cross section from its opposite ends to anintermediate zone for acceleration of flow through the intermediate zonewith consequent reduction of the static pressure of the water in theintermediate zone to substantially below atmospheric pressure;

means placing said intermediate zone in communication with theatmosphere for air flow from the atmosphere into entrainment in thewater in the intermediate zone;

said passage having a'first inwardly convergent section at one end and asecond inwardly convergent section at the other end, a first necksection adjacent the first convergent section and a second neck sectionadjacent the second convergent section, a central intermediate sectionof reduced cross section between the two neck sections, and a firstannular section between the first neck section and the central sectionand a.second annular section between the second neck section and thecentral section with said two annular sections being in communicationwith the atmosphere;

a first tubular shuttle slidingly mounted in the first neck section forlongitudinal movement between a first position retracted from thecentral section and a second position extending across the first annularsection in communication with the central section;

a second tubular shuttle slidingly mounted in the second neck sectionfor longitudinal movement between a first position retracted from thecentral section and a second position extending across the secondannular section in communication with the central section, and

said two shuttles being responsive to the opposite directions of flowthroughthe casing to cause the first shuttle to move -from its firstposition to its second position and to cause the second shuttle to movefrom its second positionto its first position in response to flowthrough the passage from the first convergent section to the secondconvergent section and to cause the first shuttle section to move fromits second position to its first position and to cause the secondshuttle to move from its first position to its second position inresponse to flow through the passage from the second convergent sectionto the first convergent section. 3. A method of aerating a relativelylarge stream of open water, characterized by the steps of:

submerging in the stream a casing having a longitudinal water passagetherethrough with an inlet end of the casing facing upstream and adischarge end facing downstream for the creation. of flow through thepassage and with the passage progressively reduced in diameter from itsinlet end to its discharge end for progressive increase in thevelocity-of flow therethrough to create a zone in the passage ofsubatmospheric pressure;

positioning said zone near the discharge end of said casing, and

placing said zone in communication with the atmosphere to cause flow ofair from the atmosphere into entrainment in the water in the zone fordischarge into the stream of open water.

4. An apparatus to aerate a stream of water comprising:

a casing forming a passage longitudinally therethrough having an inletend and a discharge end,

the passage being submerged in the stream with the inlet end of thepassage facing upstream to cause water to flow through the passage andto discharge into the stream,

the passage being reduced in diameter from its inlet end towards itsdischarge end with consequent acceleration of the velocity of the waterin the passage to create a zone of subatmospheric pressure in thepassage; 7

means placing said zone in communication with the atmosphere to causeair to flow from the atmosphere into entrainment with the water in saidzone;

said passage including at least one expansion chamber positioned betweensaid inlet end and said zone; said expansion chamber having an upstreamend and a downstream end with the downstream end being smaller in crosssection than the upstream end, and

the inner wall of said expansion chamber being curved in longitudinalcross section.

5. An apparatus as set forth in claim 4 in which a portion of saidpassage adjoining the downstream end of the expansion chamber is ofsubstantially uniform cross section.

6. An apparatus as set forth in claim 4 in which a portion of thepassage adjoining the upstream end of the expansion chamber issubstantially uniform in cross section.

7. An apparatus as set forth in claim 4 in which a portion of thepassage adjoining the downstream end of the expansion chamber and asecond portion of the passage adjoining the upstream end of theexpansionchamber are of uniform cross section.

8. An apparatus to aerate a stream of water comprismg:

a casing forming a passage longitudinally therethrough having an inletend and a discharge nd,

the passage being submerged in the stream with the inlet end of thepassage facing upstream to cause water to flow through the passage andto discharge into the stream,

the passage being reduced in diameter from its inlet end towards itsdischarge end with consequent acceleration of the velocity of the waterin the passage to create a zone of subatmospheric'pressure in thepassage;

means placing said zone in communication with the atmosphere to causeair to flow from -the atmosphere into entrainment with the water in saidzone, and i said zone positioned near the discharge end of said casing.

9. An apparatus as set forth in claim 8 in which the passage alternatelydecreases and increases in cross section between its inlet end and saidzone.

10. An apparatus as set forth in claim 4 which includes a vacuum chamberin communication both with said zone and the atmosphere, said vacuumchamber being of annular configuration and surrounding the passage, saidvacuum chamber extending upstream from said zone. I

11. An apparatus as set forth in claim 8 in which the casing terminatesin a discharge nozzle and said zone is at the upstream end of thedischarge nozzle.

12. An apparatus as set forth in claim 11 in which the length of thedischarge nozzle is not substantially more than approximately percent ofthe total length of the casing.

13. Vacuum producing means to be submerged and secured below the surfaceof a body of flowing water and comprising:

a casing with an axial passage from end-to-end forming a waterway andprovided with first and second tunnel sections, the latter being oflesser diameter than the first;

an exit tunnel section forming a nozzle end adjoining but being spacedfrom and being slightly larger than said second tunnel section andleaving an annular opening therebetween,

the casing having an annular vacuum producing chamber lying between thewaterway and the outer surface thereof;

an inlet to said chamber comprising a conduit leading therefromto thearea above the surface of the water, and an outlet from the chamberleading to said annular opening;

a tapered section at the inlet end of the casing with its smallerdiameter downstream leading to said first tunnel section; and

a larger section between the first and second tunnel sections forming anexpansion chamber, whereby the velocity of the water passing downstreamthrough the sections of decreasing diameter will increase and draw asubstantial volume of air from the area above said surface into thewaterway.

14. The structure recited in claim 13 wherein the expansion chamber hasconcavely curved walls.

15. The structure recited in claim 13 wherein the exansion h mb r's enrall s he ical in sha p 16. Tlfe gtru tu re rec ited ingzlai m 13 wherein an ad- 19. The structure recited in claim 13 wherein the tunnelsections have a venturi shape.

20. The structure recited in claim 13 wherein the casing has meanssupported by the water bed for securing the casing immovable insubmerged condition within the flowing body of water.

1. In a device for aerating open water that periodically flows inopposite directions, for example tidewater, the combination of: a casingsubmerged in the open water in longitudinal alignment with the oppositedirections of flow, said casing having a longitudinal passagetherethrough for opposite directions of flow therethrough in response tothe opposite directions of flow if the open water, said passage being ofrelatively large cross section at its opposite ends and narrowing incross section from its opposite ends to an intermediate zone foracceleration of flow through the intermediate zone with consequentreduction of the static pressure of the water in the intermediate zoneto substantially below atmospheric pressure; and means placing saidintermediate zone in communication with the atmosphere for air flow fromthe atmosphere into entrainment in the water in the intermediate zone.2. In a device for aerating open water that periodically flows inopposite directions, for example tidewater, the combination of: a casingsubmerged in the open water in longitudinal alignment with the oppositedirections of flow, said casing having a longitudinal passagetherethrough for opposite directions of flow therethrough in response tothe opposite directions of flow of the open water, said passage being ofrelatively large cross section at its opposite ends and narrowing incross section from its opposite ends to an intermediate zone foracceleration of flow through the intermediate zone with consequentreduction of the static pressure of the water in the intermediate zoneto substantially below atmospheric pressure; means placing saidintermediate zone in communication with the atmosPhere for air flow fromthe atmosphere into entrainment in the water in the intermediate zone;said passage having a first inwardly convergent section at one end and asecond inwardly convergent section at the other end, a first necksection adjacent the first convergent section and a second neck sectionadjacent the second convergent section, a central intermediate sectionof reduced cross section between the two neck sections, and a firstannular section between the first neck section and the central sectionand a second annular section between the second neck section and thecentral section with said two annular sections being in communicationwith the atmosphere; a first tubular shuttle slidingly mounted in thefirst neck section for longitudinal movement between a first positionretracted from the central section and a second position extendingacross the first annular section in communication with the centralsection; a second tubular shuttle slidingly mounted in the second necksection for longitudinal movement between a first position retractedfrom the central section and a second position extending across thesecond annular section in communication with the central section, andsaid two shuttles being responsive to the opposite directions of flowthrough the casing to cause the first shuttle to move from its firstposition to its second position and to cause the second shuttle to movefrom its second position to its first position in response to flowthrough the passage from the first convergent section to the secondconvergent section and to cause the first shuttle section to move fromits second position to its first position and to cause the secondshuttle to move from its first position to its second position inresponse to flow through the passage from the second convergent sectionto the first convergent section.
 3. A method of aerating a relativelylarge stream of open water, characterized by the steps of: submerging inthe stream a casing having a longitudinal water passage therethroughwith an inlet end of the casing facing upstream and a discharge endfacing downstream for the creation of flow through the passage and withthe passage progressively reduced in diameter from its inlet end to itsdischarge end for progressive increase in the velocity of flowtherethrough to create a zone in the passage of subatmospheric pressure;positioning said zone near the discharge end of said casing, and placingsaid zone in communication with the atmosphere to cause flow of air fromthe atmosphere into entrainment in the water in the zone for dischargeinto the stream of open water.
 4. An apparatus to aerate a stream ofwater comprising: a casing forming a passage longitudinally therethroughhaving an inlet end and a discharge end, the passage being submerged inthe stream with the inlet end of the passage facing upstream to causewater to flow through the passage and to discharge into the stream, thepassage being reduced in diameter from its inlet end towards itsdischarge end with consequent acceleration of the velocity of the waterin the passage to create a zone of subatmospheric pressure in thepassage; means placing said zone in communication with the atmosphere tocause air to flow from the atmosphere into entrainment with the water insaid zone; said passage including at least one expansion chamberpositioned between said inlet end and said zone; said expansion chamberhaving an upstream end and a downstream end with the downstream endbeing smaller in cross section than the upstream end, and the inner wallof said expansion chamber being curved in longitudinal cross section. 5.An apparatus as set forth in claim 4 in which a portion of said passageadjoining the downstream end of the expansion chamber is ofsubstantially uniform cross section.
 6. An apparatus as set forth inclaim 4 in which a portion of the passage adjoining the upstream end ofthe expansion chamber is sUbstantially uniform in cross section.
 7. Anapparatus as set forth in claim 4 in which a portion of the passageadjoining the downstream end of the expansion chamber and a secondportion of the passage adjoining the upstream end of the expansionchamber are of uniform cross section.
 8. An apparatus to aerate a streamof water comprising: a casing forming a passage longitudinallytherethrough having an inlet end and a discharge nd, the passage beingsubmerged in the stream with the inlet end of the passage facingupstream to cause water to flow through the passage and to dischargeinto the stream, the passage being reduced in diameter from its inletend towards its discharge end with consequent acceleration of thevelocity of the water in the passage to create a zone of subatmosphericpressure in the passage; means placing said zone in communication withthe atmosphere to cause air to flow from the atmosphere into entrainmentwith the water in said zone, and said zone positioned near the dischargeend of said casing.
 9. An apparatus as set forth in claim 8 in which thepassage alternately decreases and increases in cross section between itsinlet end and said zone.
 10. An apparatus as set forth in claim 4 whichincludes a vacuum chamber in communication both with said zone and theatmosphere, said vacuum chamber being of annular configuration andsurrounding the passage, said vacuum chamber extending upstream fromsaid zone.
 11. An apparatus as set forth in claim 8 in which the casingterminates in a discharge nozzle and said zone is at the upstream end ofthe discharge nozzle.
 12. An apparatus as set forth in claim 11 in whichthe length of the discharge nozzle is not substantially more thanapproximately 20 percent of the total length of the casing.
 13. Vacuumproducing means to be submerged and secured below the surface of a bodyof flowing water and comprising: a casing with an axial passage fromend-to-end forming a waterway and provided with first and second tunnelsections, the latter being of lesser diameter than the first; an exittunnel section forming a nozzle end adjoining but being spaced from andbeing slightly larger than said second tunnel section and leaving anannular opening therebetween, the casing having an annular vacuumproducing chamber lying between the waterway and the outer surfacethereof; an inlet to said chamber comprising a conduit leading therefromto the area above the surface of the water, and an outlet from thechamber leading to said annular opening; a tapered section at the inletend of the casing with its smaller diameter downstream leading to saidfirst tunnel section; and a larger section between the first and secondtunnel sections forming an expansion chamber, whereby the velocity ofthe water passing downstream through the sections of decreasing diameterwill increase and draw a substantial volume of air from the area abovesaid surface into the waterway.
 14. The structure recited in claim 13wherein the expansion chamber has concavely curved walls.
 15. Thestructure recited in claim 13 wherein the expansion chamber is generallyspherical in shape.
 16. The structure recited in claim 13 wherein anadditional tunnel section and expansion chamber is positioned betweenthe first expansion chamber and the second tunnel section.
 17. Thestructure recited in claim 13 wherein another expansion chamber andtunnel section are interposed between the first tunnel section and saidfirst mentioned expansion chamber.
 18. The structure recited in claim 13wherein the tunnel sections are of substantially uniform diameter. 19.The structure recited in claim 13 wherein the tunnel sections have aventuri shape.
 20. The structure recited in claim 13 wherein the casinghas means supported by the water bed for securing the casing immovablein submerged condition within the flowing body of water.